At the present time, improvement of industrial manufacture of long-size products is not possible without modification of the equipment serving for multihole drawing and coiling that would provide for fabrication of long-size products with residual stresses distributed symmetrically relative to the axis thereof, and, hence, for improvement of the fatigue life thereof. It is likely that most promising in this respect is a coiling apparatus designed for rectilinear drawing of the long-sized product coiled in such a manner that the moment of forces acting upon the product in a drawing-bending process should not exceed a certain critical value whereat a bending plastic strain begins.
However, the prior-art coilers widely in use do not preclude plastic bending of the long-size product during the drawing-bending process.
The coilers of the above-mentioned design are difficult to manufacture and labor-consuming in handling.
In addition, the prior-art coiling apparatus cannot provide for even drawing of the long-size product, with heavy vibration and operating instability occurring when a drawing speed of more than 60 to 70 m/min is reached, with the result that malfunctions are rather frequent.
Also known in the art is a coiling apparatus for long-size products (cf., U.S. Pat. No. 3,587,993, Cl. 242-80, dated July 10, 1971) comprising an assembly for drawing long-sized products and an assembly for coiling long-size products that are disposed separately in the direction of movement of the long-size products. In said apparatus, the assembly for drawing the long-size products comprises two rigidly-coupled shafts wherebetween the long-size product is passed.
The coiling apparatus of the foregoing design draws the long-size product by compressing it with the rolls thereof, with the result that the long-size product experiences plastic strains.